Apparatus for supplying compressed air to wash boxes



SePt- 12, 1933 A. J. SAQERS 1,926,408

APPARATUS FOR SUPPLYING COMPRESSED AIR 'l'.O WASH BOXES Filed Deo. 4, 1929 2 Sheets- Sheet 1 A. J. SAYERS Sept. 12, 1933.

APPARATUS FOR SUPPLYING COMPRESSED AIR TO WASH BOXES Filed Dec. 4, 1929 2 Sheets-Sheet 2 Patented Sept. 12, 1933 UNITED STATES VPATENT OFFICE APPARATUS FOR SUPPLYING COMPRESSED AIR T0 WASH BOXES Albert J. Sayers, Chicago, Ill., assignor to Link- Belt Company, Chicago, Ill., a corporation of Illinois Application December 4, 1929. Serial No. 411,646

4 Claims.

i "1,0 used in the past. Other objects will appear from time to time throughout the specification and claims.

In general, my invention relates to wash boxes or jigs of the so-called Baums type, wherein a *1 5 flowing bed of granular material to be treated f "2,0 material by gravity, the heavy material being at the bottom and the lighter material above, and wherein this pulsation is caused not by a reciprocating plungers working directly on the water, but by controlled intermittently released volumes of air under pressure, which itself serves as a piston for displacing the water.

Experience shows that in devices of this type the closest possible control of the pulsations and their amplitude orV intensity is essential if the best results and the-maximum capacity of the jigs are to be obtained. f

It has been customary inthe past to supply air under pressure from a positive ldisplacement blower, such as a Roots positive blower, or a piston compressor. Such devices as these, of course, provide an intermittent or pulsating flow of air and it has, in the` past been the practice to endeavor to minimize the eifect of these pulsations by having the blower or pump discharge the air into a storage tank from which it is withdrawn for supplying the jigs. This to some extent decreases the intensity of the periodic pressure variations or pulsations, but does not in actual practice equalize the pulsations or produce the desired uniform pressure. Another difliculty with devices vheretofore used is that itis frequently desirable, in any single installation, to cut out oneor more of the wash 50 boxes, if there are a number of them in operation, or to cut out the supply of air toa part or say one of the air sections of a single wash box or one or more jigs; When this is done, either air must be wasted Afrom the accumulator through 'a pressure relief valve or the 'rate at which the blower supplies air tothe accumulator must be the entire length of the box.

decreased, in either case giving an undesirable result and requiring manual control and additional installation and operating expense.

I propose to obviate the necessity of the large accumulator by providing means for furnishing .6

automatically controlled air under pressure to the jig or wash boxrby continuous flow of air without pulsation, without variation of pressure and without the necessity for a blow olf or relief valve. Thisv I accomplish by using a suitable type of centrifugal impeller air blower which has no periodicity, delivers air -under constant pressure, and will-not deliver air above a certain predetermined pressure, so that when one jig or a part of the jig is shut down and the air requirement decreased the blower itself automatically takes care of the situation.

My invention is illustrated more or less diagrammatically in the accompanying drawings, wherein- Y Figure 1 is a side elevation;

Figure 2 is a transverse section along the line 2-2 of Figure 1;

Figure 3 is a plan View;

Figure 4 is a piping diagram.

Like parts are indicated by like characters throughout the specification and drawings.

A is a jig box having a generally semi-cylin-A drical bottom Al and supported on a framework A2. The box'isusually divided into two longitudinal sectionsby a longitudinal partition A3, which extends down. into the body of the box, belowthe surface of the water contained in the box. This partition 'divides it generally into an air section and into `a material section. .The box may also be divided into three sections having air sections on each side of the material section for very wide material beds required for wash boxes of large capacity. In Figure 2 theair zone is shown on the right, the material zone or section on the left. The material section is again vdivided up into a series of air boxes A4 A4 A5 A5 by the transverse partition walls A6 and A", which extend equally as far beneath the surface of the water as does the wall A3. These air boxes are closed at their tops, as indicated by heads A8. The bottom of the-material section of the box is provided with screens A9 extending throughout screenis on two levels, and as shown the screen` is narrower and higher, as at A10, than it is at A11. Raw material is fed in through the sluice A12, into the receiving sections'of the screen, travels along the screens, and is discharged in a washed condition through the sluice4 A13,-

As shown, the l B is a screw conveyor in a trough at the bottom of the jig box, adapted to discharge refuse which passes through the screens into the elevator boots B1 B2 at either end ofthe box, these boots containing elevators, not shown, for removing the refuse. B3 B4 are adjustable gates atthe intake and discharge ends of the screen. Refuse settles to the bottom on the screens and passes out beneath these adjustable gates through the chutes B5 B6 into the elevator bootsfrom which it and the refuse from thescrewconveyor are removed from the system by the elevator buckets. When coal is being treated this refuse takes the form of dirt, clay, slate, shale, bone coal, and l the like, which is heavier than the good coal from which it is separated by gravity. 1t will be under stood that the water level is high enough above the screens so that `the entire bed of material, as it moves across the screen, is submerged ben neath the water level. l

` Associated with eachof the airsections is a quick acting valve C. This valve comprises a reciprocating piston member driven by a stem C1 througha connecting rod C2 from theeccentric C3 on the valve shaft C4. Air is supplied to each of thesevalves from a header C5through a pipe C6 controlled by a hand valve C". The valve when in one position permits a given volume of air to flow into the air section thus displacing an equal volume of water and forcing it through the screen and material and causing the latterr to stratify according to its specific gravity. The Valve when in another position cuts off the 'flow of air to the air section and permits the air under pressure to discharge to the atmosphere. The intensity of pulsation caused by the applicationof pressure in the air section and its 'release is controlled by the movement of the valve which in opening and closing sets up a pulsation in the entire mass of water associated with its particular `section of the box. Every time pressure is vapplied, the level of the water in each air section of the box is reduced, forcing water up through the screen and through the'bed of material. When the valve closes to permit the` air from each chamber to escape, the tendency, of course, for the water to return through the screen is counteracted by supplying watei` under Vpressure tion. 'a blower D7 with its valve D3.

through pipe C8, controlled by a valve C9, which water being under pressure head, rushes in to replace the water forced out by air when under pressure in the air sections. The result is that Athere is a constant pulsating now of the water which manifold is supplied with air under uniform pressure, through the pipe D controlled by a valve D1, from an air supply main D2. At each end of this main is a centrifugal blower D3 D4 Yand valves D5 D6 are associated with these blowers, so that either one may be cutout of operalntermediate the two ends of the pipe is These centrifugal blowers,v when all three of them are working, furnish air under pressure Vto Ythe system at substantially constant pressure and without pulsation, and without vibration or variation. Preferably there will be enough' of these blowers so that one or more of them' may be cut out Afor repair and adjustment, without making it necessary to shut down the system. Otherone blower.

wise, normally each blower discharges less than its maximum amount of air. If it is desired to cut out one jig or more than one jig, as the case may be, or even to cut out one air chamber in a jig, this may be done by manipulating the valves D1. When this is done, the air requirement will thereby be decreased and the centrifugal blower takes care of this change by merely discharging less air into the system, and therefore by requiring less power. to drive the blowers. Thus no accumulator is neededv and there is no exhausting through relief valve of air previously compressed Ainto the atmosphere to avoid excessive pressure.

I do not limit my invention to the use of one or more Vcentrifugal blowers. The small plant will have but one wash box and preferably but Anotherplant may have two wash boxes with airV pressure furnished by one, or two centrifugal blowers. Still another plant may have three or more wash boxes, having their air pressure supplied by one or more blowers of the proper capacity and suitable arrangement of piping and lcontrol valves.

When air is delivered by centrifugal force a constant pressure is maintained and there are no' pulsations of the air supply in the air line or to the jigs.

This absence of pulsation and pressure variation in the air supply makes it possible to adjust g the operation of the air controlrvalve for each air section 0f the jig without reference to anything except the relation between the positive controlled admission and discharge of air to the jig and the gravity separating act which it ac complishes.

Ii a positive displacement blower is used, it never can supply air except under varying pressure during each blower revolution. It becomes necessary, with a positive pressure device, to provide a large accumulator to smooth out, so far as possible, the pulsations caused by the blower. When air is forced positively under pressure in an accumulator, if one of the jigs is shut off, Aor the air supply exceeds the amount used, im. mediately the pressure on all the other jigs buildsY up until the reliefvalve reduces the pressure and these variations cause improper operation; hence the importance of the centrifugalv blower, which causes no pressure variation and which automatically takescare of the'constantly changing requirements of the jig`or jigs. f

Another very important characteristic of the centrifugal compressor or blower as distinguished from all other types of blowers or compressors is. that byY adjusting a single valve to control the -air supply to the inlet ofthe compressor Iam able to get an instantaneous response in the output of the compressor as it. is appliedtov the lhandling of material. :Experience shows that it is.

highly desirable to be able to manipulate the air supply instantaneously during operation to take Ycare of changing characteristics of the material being treated. The size of the particles, the relative dirtiness of the coal, the amount of coal being fed, all ofY them are constantly variable through greater or less range. which for best re. sults requires sudden exceedingly accurate control of the air supply, rwhich can only be given satisfactorily by controlling the supply of air to the intake of the centrifugal'compressor. If it wereiendeavoredto obtain this control by a VvalveV interposed betweenthe compressor and the jig and 'therefore subjectedto the force of the ros compressedair, such a valve would have; to be so .ponderous and massive. as to be prohibitive on the grounds of expense but even less than this, prohibitive on the grounds of lack of sensitiveness and because a valve massive enough to do the work between the compressor and the jig is so slow in operation as to be unsatisfactory.

Of course, the centrifugal air compressor with its characteristic reduction in power required when the volume of air is reduced, results in economies in operation though also it is an actual fact that the actual horse power required for maximum operation for equal air output is less with the centrifugal type than it is with any other.

I claim:

l. A plurality of air operated jig boxes, a main air supply pipe, branch pipes leading from the main pipe to each jig and a valve to control each such pipe, centrifugal air compressors at each end of and intermediate the ends of the main pipe, and a valve interposed between each cornpressor and the main pipe.

2. A plurality of air operated jig boxes, a main air supply pipe, branch pipes leading from the main pipe to each jig, and a valve to control each such pipe, centrifugal air compressors at each end of and intermediate the ends of the main pipe, and a valve interposed between each compressor and the main pipe, the capacity of said compressors being such that` anyone of them may be cut out'vof the system while permitting the remainder to furnish the entire air requirementslof the system.

3. In combination, a plurality of air actuated jig boxes, a separate Valve controlled supply pipe for each, a main supply pipe adapted to supply air under pressure to allksaid separate supply pipes, and a plurality of separate non-pulsating air compressors adapted to each separately supply air to the main pipe at separate points therealong.

4. In combination, a plurality of air actuated jig boxes, a separate valve controlled supply pipe for each, a main supply pipe adaptedto supply air underv pressure to all said separate supply pipes, and a plurality of separate non-pulsating air compressors adapted to each separately supply air to the main pipe at separate points therealong, valves adapted selectively to cut each of the compressors off from the system, the compressors being of such capacity as to be able to furnish an adequate air supply when one of them is cut oi.

ALBERT J. SAYERS. 

